The present invention relates to exchanging telecommunication traffic in a telecommunication system, comprising a satellite communication network, made up from a number of telecommunication satellites in different orbits around the earth, which are functionally connected to one or more ground stations via radio transmission connections, which ground stations are mutually connected via a transmission connection, as well as a ground communication network made up from a number of fixed and mobile telecommunication networks, in which clusters of fixed and mobile telecommunication networks are functionally connected to ground stations of the satellite communication network and telecommunication traffic is exchanged under application of an addressing plan, in which an own, unique address code is assigned to the satellite communication network.
Next to, and in addition to the known, fixed telecommunication networks, in which users can set up speech and data communication via a fixed, wire-bound connection, mobile communication via radio connections has assumed enormous proportions in recent years. Apart from differences in the applied transmission techniques, land-mobile communication is characterised by a structure, in which the coverage area of a mobile radio telecommunication network is divided into areas of geographically limited size, also called cells. Within a cell, radio traffic is possible between so-called base station and radio communication users.
On displacement of the user, a communication connection from cell to cell is continued. The geographical position of a user, i.e. the cell in which he is momentary present, is scanned regularly and stored in the system. An example of such a cellular mobile radio communication system is the xe2x80x98Global System for Mobile Communications (GSM)xe2x80x99. Systems based upon this standard are currently designated as GSM-900, GSM-1800 and GSM-1900. Other mobile telecommunication systems based on a cell structure are among other designated by the acronyms AMPS, D-AMPS in the United States and PDC in Japan. In a certain area, different mobile networks can be exploited by different operators. In general, the exploitation of mobile telecommunication networks is limited to the national boundaries. In order to enable international mobile telecommunication traffic agreements have been made between the different national operators concerning the access of subscribers to each other""s mobile telecommunication networks. The fixed telecommunication networks and the mobile telecommunication networks are connected as well, in order to enable telecommunication traffic between xe2x80x98fixedxe2x80x99 and xe2x80x98mobilexe2x80x99 users. In general, telecommunication traffic between countries is exchanged via so-called xe2x80x98International Carriersxe2x80x99 and on a global level via so-called xe2x80x98Global Carriersxe2x80x99. These are telecommunication companies that provide transmission facilities for the exchange of telecommunication traffic at international or global level, respectively.
A further communication possibility for mobile users is formed by satellite communication networks, made up from a number of telecommunication satellites in different orbits around the earth, which are functionally connected to one or more ground stations via radio transmission connections. The ground stations are dispersed over the earth in such a way, that a global coverage is achieved.
Depending on the network, the ground stations can be mutually connected via a transmission connection, e.g. in the form of a ring network. The ground stations are, in their turn, again connected to clusters of fixed and land mobile telecommunication networks, if desired, by intervention of global and international carriers.
A user provided with suitable satellite radio communication equipment, can through a direct radio connection with a telecommunication satellite and a ground station concerned, be connected to a user in a fixed or land mobile telecommunication network and of course with other users of the satellite communication network.
Satellite communication networks, which have been proposed in practice, but which are still under development, are, among others, Globalstar and Iridium, in which use is made of a relatively large number of ground stations and satellites, which circle in a low orbit around the earth, i.e. xe2x80x98Low Earth Orbit (LEO)xe2x80x99. ICO and Odyssey are satellite communication networks, in which use is made of a relatively small number of satellites, which rotate in orbits of medium altitude around the earth, also called xe2x80x98Medium Earth Orbit (MEO)xe2x80x99 satellite communication networks.
In order to be able to use the existing charging structures, it has been proposed to settle telecommunication traffic originating from and to a satellite communication network in a similar way as the land mobile telecommunication networks by intervention of global and international carriers.
As will be understood by experts, the costs of mobile telecommunication are higher than the for telecommunication traffic through the fixed telecommunication network, that has been in use for a long time. This is expressed in the higher connection charges per unit of time for mobile telecommunication traffic in comparison to fixed connections. In communication between mobile users in the same network or mutually directly connected mobile telecommunication networks and in calls of mobile users to the fixed telecommunication network, these higher call charges can be directly settled with the mobile users. To this end, the mobile telecommunication networks have been provided with suitable charging options. At the national level, the higher call charges of use of the mobile telecommunication network can also be charged to a fixed user, who requests a call to a mobile user. This is because calls from the fixed network to a mobile user take place through one or more dedicated access exchanges.
On international and global level, calls of a fixed user to a mobile user and between mobile users of non connected mobile telecommunication networks are charged on the basis of connections between two users in different countries of the fixed telecommunication network. This can be explained from the fact that for international and global connections with mobile users use is made of the same transmission routes, via international and global carriers, as for the exchange of telecommunication traffic between users connected to fixed telecommunication networks. The costs for the use of the mobile part of the connection in the mobile telecommunication network of the called mobile user are then for account of the operator of the mobile telecommunication network concerned. Depending on the tariff structure, this can with the present tariffs, quickly lead to losses in the order of USD 0,50 per minute.
Another problem arises when a mobile subscriber cannot be reached in his home network, but temporarily makes guest use of a mobile telecommunication network elsewhere, e.g. in another country.
On making a connection from a fixed to a mobile user namely, first a connection is made with the home network of the mobile user and the call is, depending on the momentary position of the mobile user, switched through to the telecommunication network where the user is located at that particular time. When the mobile subscriber concerned unexpectedly does not answer the switched-through call, switching back can take place from the mobile guest network to the mobile home network. This is done for instance to make use of a message service etc., for leaving a spoken or written message for the mobile user concerned. It will be apparent that this switching through and back, also called xe2x80x98tromboningxe2x80x99, is highly undesired due to the unnecessary use of costly transmission facilities in the telecommunication systems concerned.
The invention is aimed at providing a solution for the disadvantages and shortcomings described above which occur on exchanging telecommunication traffic between fixed and mobile telecommunication networks on both international and global level. In a first aspect, the invention provides a process for exchanging telecommunication traffic in a telecommunication system mentioned in the preamble, characterised in that a unique network address code added to the address code of the satellite communication network concerned is assigned to the mobile telecommunication systems, which are functionally connected to a ground station, in such a way that telecommunication traffic with a mobile telecommunication network is exchanged via a combination of the address code of the satellite communication network and the network address code of the mobile telecommunication network concerned via the mutually connected ground stations. The invention uses advantageously the fact that, when the ground stations of a satellite communication network are mutually connected, e.g. in the form of a ring wire, thus an alternative transmission route can be made available for the exchange of telecommunication traffic between fixed and land mobile telecommunication networks. This next to and in addition to the transmission capacity provided by international and/or global carriers, which is currently still the regular route.
By adding, according to the invention, network address codes for the mobile telecommunication networks to the unique address code of a satellite communication network, these can be directly selected via the transmission route along the ground stations of the satellite communication network, whereby direct international and global exchange of telecommunication traffic with national mobile telecommunication networks is made possible.
In departure from the existing regular route for internationally and globally exchanging telecommunication traffic between fixed and mobile networks, in which existing routing tables in the international switching centres do not allow differentiation between fixed and mobile telecommunication networks, can in this embodiment of the process according to the invention a mobile telecommunication network be addressed in a unique way. That is to say, by routing the telecommunication traffic concerned via the ground stations of the satellite communication network.
Owing to the mobile telecommunication networks being directly addressable according to the addressing or number plan of the invention, it is now possible in international and global connections of fixed users to mobile users to settle the costs of the mobile transmission part with the calling fixed user. This is also being referred to as xe2x80x98Mobile Terminating Charges (MTC).xe2x80x99
For experts it will be apparent that the addressing plan according to the invention enables very flexible operation. Operators of ground stations and/or mobile networks have with this in a very flexible way transmission capacity for the exchange of international telecommunication traffic between fixed and mobile users at their disposal, without the disadvantages of mobile transmission costs that cannot be settled.
In a further embodiment of the process according to the invention, in which the clusters of fixed and mobile communication networks are functionally connected to the ground stations of the satellite communication network via so-called transmission gateways, which transmission gateways are mutually connected via a transmission connection, it is provided that telecommunication traffic between clusters of fixed and mobile telecommunication networks is exchanged partly via the mutually connected ground stations and partly via mutually connected transmission gateways.
With this embodiment of the process according to the invention, it is possible to have the telecommunication traffic to be exchanged in the ground communication network handled partly by the regular route (international carrier/global carrier) and partly via the alternative route between the connected ground stations. With this, a very flexible routing of telecommunication traffic is obtained, also in those cases in which ground communication networks are not directly connected to a ground station of the satellite communication network. In the currently presented concept of Odyssey for instance, seven mutually connected ground stations are provided, so that clusters of fixed and land mobile telecommunication networks, via e.g. an international carrier, will be connected to the ground station in an other country.
The addressing plan according to the invention offers furthermore an effective possibility of solving the problem of tromboning. An even further embodiment of the invention provides to this end in exchanging telecommunication traffic with a user, who makes guest use of a mobile telecommunication network, by establishing a communication connection under application of the network address code concerned of the mobile telecommunication network of which the user makes guest use.
Herewith, advantageous use is made of the fact that the momentary position of a mobile user is continuously scanned and stored. By providing this information in the domain of the satellite communication network, a connection of a fixed to a mobile user can be established directly via the network address code concerned of the mobile telecommunication network where the user is located. Without first switching to the home network and thereupon switching through to the guest network. It will be appreciated that the scarce mobile transmission facilities are thus used in an efficient way.
In an even further embodiment of the process according to the invention, in which the telecommunication satellites are set up for exchanging telecommunication traffic via radio transmission connections with users, who are provided with mobile satellite radio communication equipment, mobile telecommunication traffic between mobile telecommunication networks and the satellite communication network is exchanged by establishing a communication connection under application of the network address code, which is assigned to a mobile telecommunication network concerned.
In other words, in a satellite communication network in which users can establish direct radio connections with a communication satellite, such as e.g. in the Odyssey concept, the addressing plan according to the invention is advantageously used for directly exchanging telecommunication traffic between mobile satellite communication users and land mobile users. Charging can be done according to the costs of the transmission facilities and other desired compensations.
In a second aspect the invention also provides a telecommunication system, comprising a satellite communication network, made up from a number of telecommunication satellites in different orbits around the earth, which are functionally connected to one or more ground stations via radio transmission connections, which ground stations are mutually connected via a transmission connection, as well as a ground communication network made up from a number of fixed and mobile telecommunication networks, in which clusters of fixed and mobile telecommunication networks are functionally connected to ground stations of the satellite communication network and in which the ground stations are provided with routing means for exchanging of telecommunication traffic according to an addressing plan, comprising a unique address code for selecting the satellite communication network, characterised in that the routing means are provided with selection means for exchanging telecommunication traffic with a mobile telecommunication network, under application of a unique network address code added to the address code of the satellite communication network for selecting a mobile telecommunication network concerned.
By suitable selection, mobile telecommunication traffic can be routed according to the invention via the satellite communication network, in association with a suitable charging. For charging purposes, the existing charging devices of an existing network can be applied, by means of suitable controlling according to the addressing plan according to the invention.
In the case of a telecommunication system in which the clusters of fixed and mobile communication networks are functionally connected to the ground stations via so-called transmission gateways, which transmission gateways are mutually connected via a transmission connection, in an exemplary embodiment according to the invention, routing means are provided for exchanging telecommunication traffic between clusters of mobile and fixed communication networks, partly via mutually connected transmission gateways and partly via the mutually connected ground stations.
Routing, routing means and selection means for routing telecommunication traffic are known per se to experts and do not need further clarification. For optimised routing of telecommunication traffic to users in guest networks, advantageous use is made, according to an even further embodiment of the invention, of existing signalling systems in both the satellite communication network and the ground communication network. These signalling systems are preferably based on the same standard, e.g. fully compatible with the CCITT signalling system and fitted for assessing the momentary mobile telecommunication network with which telecommunication traffic with a user concerned is to be exchanged, under application of the network address code of the mobile telecommunication network concerned.
In the most advanced embodiment of the telecommunication system according to the invention, direct mobile radio communication between satellite communication users and land mobile users is provided as well, wherein the satellite communication network and the mobile telecommunication networks are preferably based on the same standard, e.g. the GSM standard, which was mentioned before. In the concept according to the invention, the ground stations function then as xe2x80x98super mobile gateway switchesxe2x80x99, with the advantages of an optimum settlement of call charges for calls with mobile users, optimum routing and without drastic adaptations of the existing infrastructure in international switching centres, international carriers and global carriers.
It will be appreciated by experts that in the transmission connections with which the ground stations are mutually connected, one or more routing stations can be included as well. By providing these routing stations with routing means and selection means for exchanging telecommunication traffic with a connected mobile telecommunication network under application of its network address code, the same advantages can be obtained as described in the above as related to the ground stations.
In the following, the invention is described in more detail with reference to the attached